The role of the renin-angiotensin system in the control of aldosterone production will be examined in conscious rabbits. The effects of the octapeptide (angiotensin II), the heptapeptide (des-1-asp-angiotensin II) and analogues of each (sar-1-ala-8 angiotensin II and des-1-asp-isoleu-8 angiotensin II) on blood pressure, plasma renin activity, and plasma aldosterone concentration will be compared. The effects of variations in the the state of sodium balance on the responses to the octapeptide and heptapeptide will be examined in vivo. The effects of changes in sodium balance on tissue aminopeptidase activitiy will be examined. BIBLIOGRAPHIC REFERENCE: Steele, J.M. Jr., and Lowenstein, J. Differential effects of an angiotensin II analogue on pressor and adrenal receptors in the rabbit. Circ. Res. 35:593, 1974. Steele, J.M. Jr., Neusy, A-J, and Lowenstein J. The Effects of Des-1-Asp Angiotensin II on Blood Pressure, Plasma Aldosterone Concentration and Plasma Renin Activity in the Rabbit. Circ. Res. (in press).